A busload of people stood by as two Asian tourists were racially abused in the city on Easter Saturday, according to a woman who filmed the incident.

Heidi, who asked for her surname to be withheld, said a Caucasian man yelled abuse at a middle-aged man and woman of Korean descent on the 470 bus to Lilyfield, calling them ''Japanese c---s'' and ''f---ing bastards'' and saying ''why did you come to Australia?''

Yet when Heidi, a 30-year-old office worker of Chinese descent, and another Asian passenger intervened to tell the man to get off the bus, she said she received no support from other passengers.

Racist rant: A screengrab of the video posted on YouTube.

''Some told us to sit back down and be quiet and everyone just looked really blase. No one did anything about it,'' she said.

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''In fact, two girls sitting next to me thought it was funny and burst into laughter.''

A racism academic, Kevin Dunn, said bystanders had little idea what to do when they saw a racist outburst and needed better education about how to respond.

One in five people have been a victim of ''racist talk'' in Australia yet fewer than 40 per cent of bystanders will step in, a survey by Professor Dunn's challenging racism project at the University of Western Sydney found.

This included intervening, filming the incident or reporting it to an authority.

''People just don't know what they should have done - that's the number one reason for inaction,'' Professor Dunn said.

A ''data gathering portal'' will soon be launched by UWS for people to report racist incidents and receive feedback on how they responded. ''We want people to be better armed for next time,'' Professor Dunn said.

Heidi said she filmed the latter part of the rant after the abusive man refused to get off the bus. The driver can be seen instructing the man to get off the bus as he yells about the Japanese bombing of Australia during World War II and calls the Asian pair ''f---ing bastards''. It is not clear what provoked his outburst.

The incident is the latest in a string of racist rants on public transport to be filmed or shared on social media.

In February ABC newsreader Jeremy Fernandez tweeted about being called a ''black c---'' who should ''go back to his country'' by a female passenger on a Sydney bus.